1. Field of the Invention
The present invention relates to a solid-state image pick-up system, and more particularly to a solid-state image pick-up system based upon a field-sequence technique.
2. Related Art Statement
So far, various types of solid-state image pick-up systems have been proposed, which are equipped with a rotary filter conducting a color separation with a solid-state image pick-up device, and as one instance there has been known a field-sequence type solid-state image pick-up system. This field-sequence type solid-state image pick-up system separates light incident on a solid-state image pick-up device through the use of a rotary filter into R, G, and B in time sequence, with the solid-state image pick-up device outputting R, G, and B time series signals during one revolution of the rotary filter. Further, the R, G, and B signals in the time sequence are put in given memories, respectively, and the output signals are made to simultaneously occur in a manner that the reading timings thereof from the memories are set to be coincident with each other, and then delivered to a monitor or other output after undergoing a given process.
One example of arrangements of the prior field-sequence type solid-state image pick-up system will be described hereinbelow with reference to FIG. 22.
In the illustration, the solid-state image pick-up system is provided with a camera lens 2 accepting an incident light beam 1 such as a subject light beam on the front side of camera body 3, while being equipped with a R, G, and B rotary filter 4 located in the rear of the camera lens. In addition, a solid-state image pick-up device 5 is located at the back of the rotary filter 4, with the subject light beam separated through the rotary filter 4 into R, G, and B components which are incident on the solid-state image pick-up device 5.
The output signal of the solid-state image pick-up device 5 is amplified through a preamplifier 6 and then outputted through an A/D converter 12, a signal processing circuit 13 including a simultaneously generating circuit 13, a D/A converter 14 and an output terminal 15 to external equipment.
On the other hand, the camera body 3 has a synchronizing signal generating circuit 9, so that the rotary filter 4 and the solid-state image pick-up device 5 are driven by an electric motor 8 and a drive circuit 10 which operate in accordance with a synchronizing signal produced in the synchronizing signal generating circuit 9. Further, the rotation of the rotary filter 4 is detectable by means of a photointerrupter 7 disposed in the vicinity of the rotary filter 4, with the detection signal being inputted into the synchronizing signal generating circuit 9 to execute the control of rotation of the rotary filter 4. The drive circuit 10 is composed of a pulse drive circuit and a bias circuit for the drive of the solid-state image pick-up device 5.
In the field-sequence type solid-state image pick-up system with the above-mentioned arrangement, when the solid-state image pick-up device 5 outputs the R, G, and B time series signals during one revolution of the rotary filter 4, for reading out the signals from the solid-state image pick-up device 5, there are known: a first method in which group of one fields (for example, odd number fields) of the R, G, and B signals are read out therefrom at the first cycle of the rotary filter 4 whereas another group of fields (for example, even number fields) are read out therefrom at the second cycle thereof; and a second method in which both the fields of the R, G, and B signals are read out therefrom for a time period corresponding to one revolution of the rotary filter 4.
Assuming that the accumulation time for one color of R, G, and B takes 1/60 second, since according to the first method the reception of one picture is possible with 3 fields, it is possible to output 20 pictures in a period of 1 second. On the other hand, according to the second method, the reception of one picture is practicable with 6 fields so that the output of only 10 pictures is made in a period of 1 second. This signifies that both the first and second methods take 0.1 second for the reception of a picture of one frame.
Consequently, the first method is advantageous in reducing the so-called color shift which can occur because at the pick-up of a dynamic picture the subject moves during the time period of one revolution of the rotary filter 4 so that the R, G, and B differ in position.
For sensitizing in such a case as to photograph a subject with a low illuminance, there has been known a way of lengthening the accumulation time per one color as compared with the case of a subject with a common brightness. However, assuming that the accumulation time for one color is 1 second, the above-mentioned first method requires 6 seconds for the reception of one-frame picture, thus deteriorating the operating performance.